Examples of optical elements to which light is incident or from which light is emitted include: electronic devices such as semiconductor lasers, light-emitting diodes, optical sensors, and solar cells; glasses used for display; and optical members such as lenses and polarization plates.
In order that light incident to or emitted from such optical element (incident light or emission light) is not reflected by the interface between the optical element and the outside, such optical element is provided with an antireflective structure on its surface.
One of such antireflective structures is known as a “moth-eye” structure having thereon a repetition of a concave and convex structure with a cycle shorter than the wavelength of incident light or emission light in order to gradually change refractive index of light in the travelling direction of the light, thereby reducing reflectance.
As a process for producing such a structure, Patent Literature 1 discloses a process for surface treatment using a dot-arrayed metal mask.
Furthermore, Patent Literature 2 discloses a process for producing an antireflective structure by carrying out reactive etching using island-shaped metal fine particles as masks.
Furthermore, Patent Literature 3 discloses that formation of a structure larger than the wavelength of incident light (macro structure) and a structure smaller than the wavelength of incident light (micro structure) enables a moth-eye structure to yield a higher antireflective effect. The micro structure is smaller than 250 nm, and the macro structure is approximately 10 to 100 times larger than the wavelength of incident light.
Patent Literature 4 discloses a process for simply forming fine particles in such a manner that periodic patterns of highly uniformed magnetic particles are formed at once, although the fine particles are not disclosed as an antireflective structure.
Furthermore, Non-patent Literature 1 discloses a ripple shape formed on an Si substrate when the Si substrate is placed inside an ion beam sputtering device and Ar ions are radiated in a skew direction with respect to the surface of the substrate.
Furthermore, Non-patent Literature 2 discloses binary alloy phase diagrams of various elements.